The Slone Epidemiology Unit at the Boston University School of Public Health is studying the risk factors for persistent pulmonary hypertension of the newborn (PPHN). They are conducting a multi-center case-control study designed to: I) Test the hypothesis that the risk of PPHN is increased by antenatal exposure to nonsteroidal anti-inflammatory drugs (NSAIDs), particularly ibuprofen and aspirin. II) Test the hypothesis that the risk of PPHN is increased by maternal smoking during pregnancy. III) Examine relations between PPHN risk and maternal exposures to other medications, illnesses, and specific nutrients. IV) Using case-control surveillance for a wide range of birth defects, examine relations between risks of specific defects and maternal exposure to medications, illnesses and specific nutrients. V) Collect and store buccal cell samples for future analyses of the relation between PPHN risk and possible genetic marker/exposure interactions.